Wood chip cutting apparatus

ABSTRACT

Apparatus for cutting away portions of wood logs, timbers, and the like as pulp chips by means of a rotor head having a plurality of holders radiating therefrom, each carrying a bent knife to cut the wood across the grain and leave a flat surface on the wood extending substantially parallel to the direction of movement thereof. Each blade is supported outwardly thereof relative to the axis of rotation of the head, and is firmly held in precise position.

United States Patent l 13,570,567

[72] Inventor Brian D. Hickman 56] References Cited Crofion, Columbia, Canada P [211 P 806935 2,938,553 /1960 Standal 144/224 [22] 131969 3 282 312 11/1966 St d 1 144/220 Patented 16,1971 a a [73] Assignee MacMillan Bloedel Limited Primary Examiner-Donald R. Schran Vancouver, British Columbia, Canada Att0rneyFetherstonhaugh and Co.

[54] wool.) CUT'FINSAPPARATUS ABSTRACT: Apparatus for cutting away portions of wood 23 Chums 1 Drawmg logs, timbers, and the like as pulp chips by means of a rotor [52] 0.8. CI 144/220, head having a plurality of holders radiating therefrom, each 144/162 carrying a bent knife to cut the wood across the grain and [51] Int. Cl B27g 13/04 leave a flat surface on the wood extending substantially paral- Field of Search 144/235, lel to the direction of movement thereof. Each blade is supl/( nq ir ported outwardly thereof relative to the axis of rotation of the 4 14 /218 head, and is firmly held in precise position.

Patented March 16, 1.971 3,570,567

6 Sheets-Sheet 1 Patented March 16,, 1971 3,570,567

6 Sheets-Sheet :5-

flaw Md fir ATTORNEYS Patented March 16,1971

6 Sheets-Sheet 4 woon c: 1ft" CUT'i'llNG Arrrus BACKGROUND or THE INVENTION This invention relates to apparatus for cutting away portions of wood logs, timbers, and the like as pulp chips by means of one or more bent knives and leaving flat surfaces on the wood.

The knives used in this apparatus are well known in the industry. Each knife has a grain severing flank, and a finishing flank extending at an angle to the grain flank. In other words, the knife or blade is roughly L-shaped, consisting of the two flanks, one of which extends at an obtuse angle to the other. The two flanks may be welded together at the corner or joint therebetween, but they are preferably made from a single piece of steel bent to the desired shape. The knife has a cutting edge which extends from substantially the outer or free end of one flank to the outer or free end of the other flank.

With the holder commonly used prior to this invention, the knife is pressed against an outer surface of the holder which is roughly L-shaped the same as the knife. A clamping plate is shaped to fit over the knife from end to end thereof and is bolted to the holder. As a result, the knife is pressed against the shaped holder outer surface. If the knife angle is not exactly correct, a very frequent occurence unless expensive close tolerances are maintained in the manufacture thereof, the knife is bent to conform to the holder surface by the clamping plate. This results in high bending tensions in the knife at the joint or corner thereof, and this very frequently results in breakage. In addition, the clamping plate is bent at an angle similar to the knife so that when the plate is bolted down at its ends, it tends to bow between said ends so that the knife is not securely held along the grain flank which is subjected to the greatest force and wear. Furthermore, the chips cut away from the wood strike the holder itself, subjecting it to a great deal of wear, and this makes it necessary frequently to replace holders at relatively great expense in time and material. Another disadvantage of the prior holding apparatus results from the fact that the clamping plate is outside the knife so that if the bolts are accidentally left untightened, centrifugal force may throw the clamping plate and the blade outwardly with the resulting danger to anyone or anything in the vicinity of the apparatus. The prior holders are also relatively heavy, and this causes problems because of the fact that the holders are mounted on the rim of a hub that has to turn at high speed. The mass moment of inertia of the previous holder is relatively great. This necessitates relatively high horsepower requirements on variable speed applications, and results in considerable damage to the holders and the accompanying elements thereof in the event of a wreck or the foul up of the cutting operation.

SUMMARY OF THE INVENTION The cutting apparatus of the present invention eliminates or greatly reduces the problems set out above. With this apparatus, one flank only, usually the grain severing flank, is clamped to an inner surface of the knife holder by a clamping plate. Guide means are provided on the holder within which the outer edges of the grain flank and the finishing flank are retained to maintain the knife in alignment. When the clamping plate is clamped against the knife flank by bolts which pass through slots in the knife, the knife is not subjected to any bending stresses so that it lasts many times longer than one clamped in the prior holders. Thus, the knives do not have to be kept within expensive close tolerances during manufacture. In the new holder, the wood chips are directed against the clamping plate so that when the latter has been subjected to considerable erosion, it can be quickly, easily and inexpensively replaced, instead of the entire holder. As the blade and clamping plate are within the holder, and as the clamping plate is positively located against motion in normally anticipated directions, if the bolts are accidentally left untightened, centrifugal forceholds these elements in place so that they are not likely to fly outwardly to cause danger to nearby persons and equipment. In the preferred form of this ing working on the inner surfaces thereof during manufacture.-

As a result, alloy steels of great strength can be used since it is possible to get at the inner surfaces to use known high accura cy and improved rate of production processes. Furthennore, the various elements of the holder can be made lighter so that these holders are considerably lighter than the prior holders. This holder has reduced mass moment of inertia, and this results in reduced horsepower requirements on variable speed applications, and in the event of a wreck, reduced damage to the holder, its hub, shaft, bearings and other adjacent components.

The construction of the present holder makes it possible to extend bolts from the holder through slots in the knife and into the clamping plate, thus making a very strong unit so that the weight of the clamping plate and holder can be considerably reduced without materially reducing the knife support. Knives and apparatus of this type are changed frequently for grinding which results in wear of the bolts and the tapped holes. In the present apparatus, the tapped holes subjected to frequent use and wear are in the clamping plates, and the latter can be quickly and easily replaced when necessary without too much expense. 1

Apparatus according to the present invention comprises a hub having a rim, a knife holder secured to the hub and having an inner clamping surface spaced from the rim thereof and against which an outer surface of the grain severing flank of a knife bears, a clamping plate against an inner surface of the knife, bolt means for clamping the plate, knife and bolder together, first guide means on the holder close to the outer end of the grain flank, and second guide means close to the outer end of the finishing flank, said first and second guide means retaining the knife in place when the bolt means permit movement thereof. During operation, the grain flank of the knife cuts across the grain of the wood, while the finishing flank moves through the wood substantially parallel to the grain thereof to leave a flat surface thereon. In other words, the grain flank cutting across the grain of the wood forms the chips, while the other flank trims the surface of the wood at the end of the chip-forming cut. The outer surface of the finishing flank is not clamped against any surface of the holder, and said second guide means is designed to provide said finishing flank with a certain amount of support. Thus, when the knife is clamped in the apparatus, it is not subjected to any bending stress, and there is nothing to cause the clamping 7 plate to bow when the elements are tightly clamped together.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 diagrammatically illustrates cutting apparatus according to the present invention;

FIG. 2 diagrammatically illustrates the cutting action of the bent knifes of the type used in this apparatus;

FIG. 3 is an enlarged fragmentary front elevation of the cutting apparatus, in which position the illustrated knife holder is tipped back relative to the face of the rotor of the apparatus;

FIG. 4 is a view similar to FIG. 3 with the cover plate removed, but with the rotor of the apparatus tipped back so that the knife holder is seen in end elevation;

FIG. 5 shows the opposite end of the knife holder from that seen in FIG. 4;

FIG. 6 is a sectional view taken substantially on the line 6-6 of FIG. 3;

EKG. '7 is a plan view of the cutting apparatus showing one knife holder only, the rest of the holders being omitted for the sake of clarity;

PK 8 is an enlarged sectional view taken on the line 8-% of FIG. 5;

FIG. 9is a sectional view taken on line 9-8 of FIG. 7;

FIG. it) is a section taken on the line 10-10 of FIG. 5, showing only the knife;

FIG. 11 is a perspective view of the hub and rim alone of the apparatus;

FIG. 12 is an end elevation similar to FIG. 3 of an alternative form of cutting apparatus according to this invention; and

FIG. 13 is a view of the rear end of one of the knife holders of the alternative form of apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. 1 and 2 of the drawings, cutting apparatus includes a rotor head 12 fixedly mounted on a drive shaft 13 which is rotated in any suitable manner, such as by means of a heavy duty electric motor 14. Rotor 12 has a plurality of cutting elements 17 radiating therefrom. The rotor head and its cutting elements are usually partially enclosed in a hood for catching the wood chips and directing them away from the apparatus, but this hood has been omitted from the drawings for the sake of clarity. Logs, timbers or other pieces of wood are moved past head 12 of the apparatus to have portions thereof converted into pulp chips. For example, a log 20 is moved past head 12 in any suitable manner, such as by a sawmill carriage, not shown, and the side or slab portion 21 thereof, see FIG. 2, is removed as chips, leaving a flat surface 22 on the wood.

Each cutting element 17 supports a bent knife 25 having a grain severing flank 26 and a finishing flank 27 angled relative thereto. In FIG. 2, two knives only are diagrammatically shown where they contact log 20 in order to illustrate the cutting action of apparatus 10. During operation, head 12 rotates in the direction of arrow 29 in FIG. 1 and arrow 3% in FIG. 2 which means that the knife at the right in the latter FIG. is moving downwardly. Log 20 moves in the direction of arrow 31. As knife 25 moves downwardly through the wood, grain severing flank 26 cuts away a piece of wood 34, and as this flank extends generally across the grain of the log, piece 34 tends to break into chips 35, the grain fibre length of which depends upon the depth of the cut made by flank 26, and this depends upon the speed of rotation of head 12 and the rate of movement of log 20 past the head. Finishing flank 27 of the knife moves downwardly through the wood substantially parallel to the grain thereof to act somewhat like a plane moving over surface 22 of the log and leaving a comparatively smooth surface.

As the cutting elements 17 are the same, only one will now be described in detail.

Referring now particularly to FIGS. 3 to 11 of the drawings, rotor head 12 includes a hub 40 having a rim 41 connected thereto by a web 42. Hub 4% is mounted on drive shaft 13 in any convenient manner. In this example, the shaft is formed with a tapered section 45 at its outer end, see HQ. 6, and hub 40 has a correspondingly tapered core 46 which fits on shaft section 45 and is caused to rotate therewith any convenient manner, such as by a key 47. A retaining plate 48 is bolted to the outer end of shaft section 45, and bears against a shoulder 49 formed in hub 40 to keep the latter on the shaft.

By referring to FIG. 6, it will be seen that rim 41 is relatively wide, and that hub 40 is longer than the width of the rim. A

cover plate 52 surrounds shaft 48 and is bolted to the outer edge of rim 41 and the outer end of hub 40 by bolts 53 and 54, respectively. Plate 52 has an annular section 55 projecting beyond rim 41, said section having notches 56 therein, one for each cutting element 17. This plate prevents log 20 from moving axially relative to head 12, and it prevents chips and dirt from getting into the space between the hub and the rim. A strong and relatively large supporting disc 57 surrounds shaft 13 and is secured to the inner end of hub 40 by bolts 58. Disc 57 has lightening holes 59 therein, see FIG. 5.

A plurality of lugs 62 are mounted on the outer surface of rim 41, there being one of these lugs for each cutting element 17. Each lug 62 extends across the surface of rim 41 at an angle, as clearly shown in FIGS. 7 and 11. The forward end 64 of each lug is located at the outer edge 65 of the rim, while the rearward end 66 of the lug is located near the inner rim edge 67. During operation, rotor head 12 rotates in the direction of arrows 69, 70, and 71 of FIGS. 3, 5 and 6 respectively. Lug 62 has a keyway 74 in its side surface 75, and it has a plurality of bolt holes 76 therethrough, there being three bolt holes in the illustrated lug.

Each cutting element 17 includes a knife holder 79 which has somewhat the same shape as a knife 25, that is, it has back section 81 and a relatively short side section 82 extending away from one end of the back section at an angle thereto, as clearly shown in FIGS. 4 and 6. Side section 82 of the holder is located at one of the notches 56 of cover plate 52. The side section has a flat inner surface 84 which bears against the flat side surface 75 of a lug 62 over keyway 74 thereof, said side section having a keyway 86 therein matching keyway 74. A key 87 tits in keyways 74 and 86, and bolts 89 extend through lug holes 76 and are threaded into tapped holes 90 in side section 82 of the holder firmly to secure the latter to lug 62.

By referring to FIGS. 4, 5 and 6, it will be seen that side section 82 of the holder radiates outwardly from rim 4] and extends across the outer surface thereof at an angle thereto, the same angle as lug 62. The back section 81 of the holder is inclined outwardly in a radial direction from the rim and extends thereover from near the rim outer edge 65 and terminates above and inwardly of its inner edge 67. Actually, end 92 of holder 79 is positioned above the outer edge of supporting disc 57. This holder end 92 has a flat'surface 93, see FIGS. 5 and 9, extending substantially parallel to the axis of rotation of the rotor head and facing inwardly thereof, this surface bearing against a corresponding flat surface 95 on the outer end of a spoke 96 which is secured at its inner end 97 to supporting disc 57 near the edge thereof. Holder end 92 has a plurality of holes 100 therein, there being two of these holes in the illustrated example, and bolts 101 extend through these holes and are threaded into tapped holes 102 in the outer end of spoke 96. Thus, lug 62 supports side section 82 of holder 79, while spoke 96 supports end 92 thereof. It will be noted that each holder 79 is outwardly of and extends across the outer surface of rim 41 at an angle to the axis of the rotation of rotor head 12, said axis being indicated at 104 in FIG. 7. As a result of this, the end 92 of the holder is ahead of the opposite end thereof with reference to the direction of rotation of the rotor head.

By referring to FIGS. 4, 5 and 6, it will be seen that spoke 96 is angularly mounted on disc 57 and curves outwardly at 105 near its inner end. This forms a relatively large pocket or channel 107 within holder 79 that is located outwardly of the outer surfaces of rim 41 and supporting disc 57. Cover plates 109 are bolted to outer edges of lugs 62 and the outer surface of disc 57 to form the inner wall of each channel 107 and to prevent chips and dirt from getting into the space between web 42 and disc 57.

l-Iolder 79 has an inner flat clamping surface against which grain flank 26 of blade 25 bears. The outer or free end of the grain flank is close to a guide shoulder 117 formed in holder 79 at the outer end of surface 115. The finishing flank 27 of the blade extends along but is slightly spaced from the inner surface of side section 82 of the holder, and the outer or free end of this finishing flank is close to a guide shoulder 119. It is desirable to incline this shoulder relative to the inner surface of section 82 so that shoulders 117 and 119 are parallel. The outer surface of blade flank 27 is chamfered as indicated at 12 in FIGS. 4,5 and 9 parallel to the adjacent shoulder 119. A clamping plate 123 overlies grain flank 26, and bolts 125 extend through holes 126 in back section 81 of the holder, through slots 127 in knife flank 26, and are threaded in tapped holes 128 in clamping plate 123. It will be noted that the heads of bolts 125 are located in depressions 131 in the outer surface of hoider back section 811. Guide shoulders 117 and 119 are substantially parallel to each other and to the axes of bolts 125 so that when the latter are tightened, the knife moves along said shoulders towards the flat clamping surface of the holder back section.

Blade 25 has a cutting edge 135 along an edge thereof, said cutting edge extending throughout the grain and finishing flanks, and the blade also has a back edge 136, see FIG. 10. Clamping plate 123 has a shoulder 139 which overlaps the back edge 136 of the knife along the grain flank 26 thereof, and this shoulder is formed with a key 1 511 which fits into a slot 141 formed in the back section of holder 79, see FIG. b. .When bolts 125 are loose, knife 25 is shifted so that its cutting edge 135 projects beyond adjacent edges 143 and 1 34 of back section 81 and clamp 123. From F161. 3 it will be seen that the outer surface of section 81 is chamfered as at 146, while the outer surface of clamping plate 123 is chamfered as at 147 so that said back section and said plate are inclined inwardly towards the cutting edge of the knife. Plate 123 is also chamfered or inclined inwardly in the direction away from chamfer 14 and towards the back edge of the plate, as indicated at 1 18. After each sharpening of knife 25, a babbitt slug 1511 is cast on to edge 136 of the blade, see FIGS. 8 and 111, said slug filling the space between this edge and shoulder 139 of clamping plate 123. In actual practice, a make-up piece 151 is screwed to the inner surface of shoulder 139 to act as the effective inner surface thereof. The blade is formed with two inclined slots 152 extending inwardly from blade edge 136 so that when the babbitt slug is poured, some of the metal runs into these slots to anchor the slug in proper place relative to the knife. This is .done in a jig made for this purpose. The slug, bearing against. make-up piece 151 of the clamping plate shoulder, keeps the cutting edge of the knife projecting the correct distance from the holder.

The operation of apparatus 10 is quite simple. As rotor head 12 is rotated by motor 14 the cutting elements 17 move successively downwardly through log 20 cutting away portions of the side material thereof as chips, as diagrammatically illustrated in FIG. 2. As each knife holder 79 moves downwardly towards the wood, the cutting edge 135 of its knife cuts into the wood. The portion of the cutting edge extending along grain flank 26 cuts substantially across the grain of the wood, while the portion of the cutting edge extending along finishing section 27 severs the inner end of the portion cut by the grain flank from the rest of the wood and smooths off surface 22 of the log. it will be noted that the part of cutting edge 135 extending along the finishing flank of the knife extends through cover notch 56 slightly outwardly of cover 52 and substantially parallel to the latter. The chips fly through channel 107 and are gathered by a hood, not shown, which nonnally surrounds head 12. Clamping plate 123 is subjected to the oresive action of these chips, and when it has worn to a certain degree, it can quickly and easily be changed. Bolts 125 have to be loosened each time the blade is sharpened, and as these bolts are threaded into holes 128 of the clamping plate, the latter may be changed if the threads of the tapped holes become worn.

A very important feature of this invention is that the grain flank 26 of the blade is clamped against the flat inner surface 115 of back section 81 of holder 79. As plate 123 clamps this portion of the blade against said flat surface, and this is the only clamping action for the blade, there is no tendency of the clamping plate to bow so that the blade is firmly held in position. in addition, finishing flank 27 does not bear against the inner surface of side section 82 of the holder so that said finishing flank is not subjected to any strain when the knife is clamped in position. Guide shoulders 117 and 119 keep the knife properly aligned on holder 79 when bolts 12$ are loose. As holder back section :81, blade flank 26 and clamping plate 123 are clamped together as a unit by bolts 125, these elements, which have to withstand the maximum strain during operation, can be made relatively thin and light. if bolts 125 are not tightened as much as they should be, knife 25 and clamping plate 123 still remain in proper position during operation since centrifugal force moves the clamping plate against the blade flank and the latter against the clamping surface 115 of the holder so that there is little danger of them flying away from the head. As the holder 79 is separate from lug 62 and spoke 96, it can be milled on is inner surface during manufacture.

I progressively towards the curved joint or bend of the blade edge at the outer end of flank 27 is ahead, with reference to the direction of rotation of head 12 indicated by arrow 69, of the bend of the blade.

As lug 62 is inclined across the outer surface of rim d1, cutting edge of the knife extending along finishing flank. 27 is substantially in line with the outer surface of cover 52, see FIGS. 3 and 6. The annular section 55 of face plate 52 ex-- tends outwardly to the end of knife flank 27. One of the functions of this plate is to prevent lateral motion of the log towards the rotor head. The closer plate 52 is to the cutting knives, the sooner this lateral motion is stopped.

The flaring and twisting of spokes 96 at 105 makes the exit end of channel 107 larger than the entrance end thereof at the cutting edge of the knife. This provides increased space through which the cut chips may flow, creates windage to aid chip clearance, and aids in clearing chips which may not travel directly through the holder but have been carried radially against the surface 148 of clamping plate 123 by centrifugal force. As this surface flares outwardly towards the exit end of the channel, the chips will slide along this surface under the action of centrifugal force rather than be held thereon.

Although it is preferable to use'spokes as described above, these spokes can be omitted if the remaining elements are made strong enough to stand up to the forces actingagainst the knives during operation. This arrangement is most practical when flank 26 is relatively short and the distance from the outer surface of the log to the flat surface 22 thereof is small.

F165. 12 and 13 illustrate an alternative form of the invention. Cutting apparatus 10a includes cutting elements 17a which are complete units themselves, and each is mounted on a flat surface 169 of a hub rim 161.

Each cutting element 17a includes a base secured to rim 161 in any suitable manner, such as by bolts 166. Unit 17a also includes a knife holder 168. This holder comprises a back section 171), and a side section 171 connected to an end thereof and extending at an angle thereto. Back section 170 has a flat clamping surface 173, while side section 171 has an inner surface 17a. The grain flank 26 of knife 25 is clamped against said surface 173 by clamping plate 176 in the same manner as in apparatus 10. Parallel guide surfaces or shoulders 171i and 179 are provided near the outer ends of the holder back section and side section, and the free ends of the grain flank and the finishing flank of the knife are positioned near these surfaces respectively. Surfaces 178 and 179 are substantially parallel to each other and to the clamping bolts 180 of plate 176.

The main difference between apparatus 11) and apparatus 10a is that in the latter, the free end of side section 171 of the holder is secured to base 165 at 182 in any suitable manner. The opposite or outer end of back section 176, instead of being removably connected to a spoke, is integrally connected to a brace or wall 1%5 which extends inwardly therefrom and is connected at its opposite end to base 165 at 186. In actual practice, base 165, back section 170, side section 171 and brace or wall 185 are cast together to form a one-piece unit or holder which is bolted on to the flat. surface 166 of hub rim 161. This unit has extending therethrough a pocket or channel 189 through which chips flow during operation of the apparatus. Front HQ. 13 it will be seen that wall 135 is inclined inwardly from the back end 1911 of holder 16% towards the front end of the holder and the cutting edge of the knife, as indicated at 192 in FIG. 13. Thus, channel 1%) increases in cross-sectional area towards the back end of the holder so as to provide an enlarged area for the chips to travel through. As clamping plate 176 is the same as clamping plate 123 of apparatus 10, the former is formed with an inclined surface 194 which extends towards the back end of channel 189 so that chips are directed towards the exit end of the channel by centrifugal force.

Apparatus a of H68. 12 and 13 has most ,of the advantages pointed out above in connection with apparatus 10. However, apparatus 10a is heavier than the other, and as base 165, holder 170 and brace 185 are formed in a single unit, it is more-difficult to do the necessary cutting on the inner surface of the knife holder during manufacture.

I claim:

1. Apparatus for cutting away portions of wood logs and the like as pulp chips by means of one or more bent knives and leaving flat surfaces on the wood, comprising at least one knife having a grain severing flank and a finishing flank extending at an angle to said grain flank, a hub having a rim, a knife holder secured to the hub and having an inner clamping surface extending generally axially of the hub and spaced from the rim thereof and against which an outer surface of the grain flank of the knife bears, a clamping plate against an inner' surface of said knife grain flank, bolt means for clamping said holder, knife and'plate together, first guide means on the holder at the outer end of the grain flank, and second guide means on the holder at the outer end of the finishing flank, said first and second guide means keeping the knife in place when said bolt means permits movement thereof and not interfering when the bolt means is tightened.

2. Cutting apparatus as claimed in claim 1 in which said knife holder includes a side section secured to said rim near an outer edge thereof and radiating therefrom, and a back section connected to the side section and spaced outwardly from and extending across said rim, said inner clamping surface being on the back section, and said side section having an inner surface extending substantially parallel to said outer edge of the rim and along which the knife finishing flank extends in spaced relationship.

3. Cutting apparatus as claimed in claim 2 in which said first guide means comprises a shoulder on the back section substantially parallel to said bolt means and substantially normal to said inner clamping surface of the back section.

4. Cutting apparatus as claimed in claim 3 in which said second guide means comprises a shoulder in the side section substantially parallel to said bolt means and said first guide means shoulder and at an angle to said inner surface of the side section.

5. Cutting apparatus as claimed in claim 2 in which said back section is inclined outwardly in a radial direction from said side section.

6. Cutting apparatus as claimed in claim 5 in which said back section is inclined forwardly from said side section with reference to the direction of rotation of the rim.

7. Cutting apparatus as claimed in claim 2 including a lug on and radiating from said rim and to which said side section is removably connected.

8. Cutting apparatus as claimed in claim 7 in which said lug has an end near the outer edge of the rim, said lug extending across the rim and rearwardly with reference to the direction of rotation of the rim.

9. Cutting apparatus as claimed in claim 1 in which said bolt means comprises a plurality of bolts extending through said holder, slots in the grain flank of the knife, and into the clamping plate.

10. Cutting apparatus as claimed in claim 2 including a spoke connected to and radiating from the hub to the opposite end of the back section from said side section, and means removably connecting said opposite end of the back section to said outer end of the spoke.

11. Cutting apparatus as claimed in claim 2 including a supporting disc connected to the hub inwardly of the rim thereof, a spoke connected to said disc and radiating therefrom to the opposite end of the back section from said side section and means removably connecting said opposite end of theback section to said outer end of the spoke, said back and side sections and the spoke forming an inner channel through which chips cut by the knife can travel.

12. Cutting apparatus as claimed in claim 11 including cover means between the rim and the supporting disc and forming a wall of said channel.

13. Cutting apparatus as claimed in claim 11 in which said channel has an entrance end-near said knife and an opposite exit end, and said spoke is bent outwardly relative to the channel so as to make said exit end of the channel larger than the entrance thereof.

14. Cutting apparatus as claimed in claim 13 in which the surface of said clamping plate is inclined towards said exit end of the passage so that chips on said inclined surface slide towards the exit end under the action of centrifugal force.

15. Cutting apparatus as claimed in claim 2 including a lug on and radiating from said rim, said side section overlapping the lug, and bolt means through and removably securing together the lug and the side section.

16. Cutting apparatus as claimed in claim 2 in which said clamping plate has a shoulder overlapping a rearward edge of the grain flank of the knife, and including means between said shoulder and said rearward edge of the grain flank for maintaining the knife in proper cutting position between the clamping plate and the knife holder.

17. Cutting apparatus as claimed in claim 16 in which said knife maintaining means is adjustable so as to maintain said knife in proper cutting position after the knife has been sharpened.

18. Cutting apparatus as claimed in claim 2 in which said side section of the holder is connected to a base, and said base is removably secured to the rim.

19. Cutting apparatus as claimed in claim 18 including a brace radiating from said base and connected at one end to the latter and at its opposite end to the opposite end of the back section from the side section of the holder.

20. Cutting apparatus as claimed in claim 19 in which said first guide means comprises a shoulder on the back section substantially parallel to said bolt means and substantially normal to said inner clamping surface.

21. Cutting apparatus as claimed in claim 20 in which said second guide means comprises a shoulder on the side section substantially parallel to said bolt means and said first guide means shoulder and at an angle to said inner surface of the side section.

22. Cutting apparatus as claimed in claim 19 in which said clamping plate has a shoulder overlapping a rearward edge of the grain flank of the knife, and including means between said shoulder and said rearward edge of the grain flank for maintaining the knife in proper cutting position between the clamping plate and the knife holder.

23. Cutting apparatus as claimed in claim 22 in which said knife maintaining means is adjustable so as to maintain said knife in proper cutting position after the knife has been sharpened. 

1. Apparatus for cutting away portions of wood logs and the like as pulp chips by means of one or more bent knives and leaving flat surfaces on the wood, comprising at least one knife having a grain severing flank and a finishing flank extending at an angle to said grain flank, a hub having a rim, a knife holder secured to the hub and having an inner clamping surface extending generally axially of the hub and spaced from the rim thereof and against which an outer surface of the grain flank of the knife bears, a clamping plate against an inner surface of said knife grain flank, bolt means for clamping said holder, knife and plate together, first guide means on the holder at the outer end of the grain flank, and second guide means on the holder at the outer end of the finishing flank, said first and second guide means keeping the knife in place when said bolt means permits movement thereof and not interfering when the bolt means is tightened.
 2. Cutting apparatus as claimed in claim 1 in which said knife holder includes a side section secured to said rim near an outer edge thereof and radiating therefrom, and a back section connected to the side section and spaced outwardly from and extending across said rim, said inner clamping surface being on the back section, and said side section having an inner surface extending substantially parallel to said outer edge of the rim and along which the knife finishing flank extends in spaced relationship.
 3. Cutting apparatus as claimed in claim 2 in which said first guide means comprises a shoulder on the back section substantially parallel to said bolt means and substantially normal to said inner clamping surface of the back section.
 4. Cutting apparatus as claimed in claim 3 in which said second guide means comprises a shoulder in the side section substantially parallel to said bolt means and said first guide means shoulder and at an angle to said inner surface of the side section.
 5. Cutting apparatus as claimed in claim 2 in which said back section is inclined outwardly in a radial direction from said side section.
 6. Cutting apparatus as claimed in claim 5 in which said back section is inclined forwardly from said side section with reference to the direction of rotation of the rim.
 7. Cutting apparatus as claimed in claim 2 including a lug on and radiating from said rim and to which said side section is removably connected.
 8. Cutting apparatus as claimed in claim 7 in which said lug has an end near the outer edge of the rim, said lug extending across the rim and rearwardly with reference to the direction of rotation of the rim.
 9. Cutting apparatus as claimed in claim 1 in which said bolt means comprises a plurality of bolts extending through said holder, slots in the grain flank of the knife, and into the clamping plate.
 10. Cutting apparatus as claimed in claim 2 including a spoke connected to and radiating from the hub to the opposite end of the back section from said side section, and means removably connecting said opposite end of the back section to said outer end of the spoke.
 11. Cutting apparatus as claimed in claim 2 including a supporting disc connected to the hub inwardly of the rim thereof, a spoke connected to said disc and radiating therefrom to the opposite end of the back section from said side section, and means removably connecting said opposite end of the back section to said outer end of the spoke, said back and side sections and the spoke forming an inner channel through which chips cut by the knife can travel.
 12. Cutting apparatus as claimed in claim 11 including cover means between the rim and the supporting disc and forming a wall of said channel.
 13. Cutting apparatus as claimed in claim 11 in which said channel has an entrance end near said knife and an opposite exit end, and said spoke is bent outwardly relative to the channel so as to make said exit end of the channel larger than the entrance thereof.
 14. Cutting apparatus as claimed in claim 13 in which the surface of said clamping plate is inclined towards said exit end of the passage so that chips on said inclined surface slide towards the exit end under the action of centrifugal force.
 15. Cutting apparatus as claimed in claim 2 including a lug on and radiating from said rim, said side section overlapping the lug, and bolt means through and removably securing together the lug and the side section.
 16. Cutting apparatus as claimed in claim 2 in which said clamping plate has a shoulder overlapping a rearward edge of the grain flank of the knife, and including means between said shoulder and said rearward edge of the grain flank for maintaining the knife in proper cutting position between the clamping plate and the knife holder.
 17. Cutting apparatus as claimed in claim 16 in which said knife maintaining means is adjustable so as to maintain said knife in proper cutting position after the knife has been sharpened.
 18. CUtting apparatus as claimed in claim 2 in which said side section of the holder is connected to a base, and said base is removably secured to the rim.
 19. Cutting apparatus as claimed in claim 18 including a brace radiating from said base and connected at one end to the latter and at its opposite end to the opposite end of the back section from the side section of the holder.
 20. Cutting apparatus as claimed in claim 19 in which said first guide means comprises a shoulder on the back section substantially parallel to said bolt means and substantially normal to said inner clamping surface.
 21. Cutting apparatus as claimed in claim 20 in which said second guide means comprises a shoulder on the side section substantially parallel to said bolt means and said first guide means shoulder and at an angle to said inner surface of the side section.
 22. Cutting apparatus as claimed in claim 19 in which said clamping plate has a shoulder overlapping a rearward edge of the grain flank of the knife, and including means between said shoulder and said rearward edge of the grain flank for maintaining the knife in proper cutting position between the clamping plate and the knife holder.
 23. Cutting apparatus as claimed in claim 22 in which said knife maintaining means is adjustable so as to maintain said knife in proper cutting position after the knife has been sharpened. 